Contents

The 16 in/45 were improved versions of the Mark 5 guns mounted on the Colorado-class battleships, with their limit of a 2,240-pound (1,020 kg) shell with a maximum 35,000-yard (32,000 m) range at their turret limit of 30-degree elevation.[1] A major alteration from the older guns was the Mark 6's ability to fire a new 2,700-pound (1,200 kg) armor-piercing (AP) shell developed by the Bureau of Ordnance. At full charge with a brand-new gun, the heavy shell would be expelled at a muzzle velocity of 2,300 feet per second (700 m/s); at a reduced charge, the same shell would be fired at 1,800 f/s (550 m/s).

Turning at 4 degrees a second, each turret could train to 150 degrees on either side of the ship. The guns could be elevated to a maximum elevation of 45 degrees; turrets one and three could depress to −2 degrees, but due to its superfiring position, the guns on turret two could only depress to 0 degrees.[3]

When firing the same shell, the 16 in/45 Mark 6 had a slight advantage over the 16 in/50 Mark 7 when hitting deck armor—a shell from a 45 cal gun would be slower, meaning that it would have a steeper trajectory as it descended. At 35,000 yards (20 mi; 32 km), a shell from a 45 cal would strike a ship at an angle of 45.2 degrees, as opposed to 36 degrees with the 50 cal.[3]

A cut-away diagram of the 16-inch turrets on board the North Carolina class

The Mark 6 and 7 guns were originally intended to fire the relatively light 2,240-pound (1,020 kg) (1.00 long ton) Mark 5 armor-piercing shell. However, the shell-handling system for these guns was redesigned to use the "super-heavy" 2,700-pound (1,200 kg) APCBC (armor-piercing, capped, ballistic capped) Mark 8 shell before any of the Iowa-classbattleships were laid down. The large-caliber guns were designed to fire two different 16-inch (406 mm) shells: an armor-piercing round for anti-ship and anti-structure work, and a high-explosive round designed for use against unarmored targets and shore bombardment.

The Mark 8 shells gave the North Carolina, South Dakota, and Iowa classes the second heaviest broadside of all battleship classes, despite the fact that the North Carolina and South Dakota ships were treaty battleships. Only the Yamato-classsuper dreadnoughts could throw more weight. The Mark 6's disadvantage relative to other contemporary battleship classes was its comparatively shorter range.[3][4]

The propellant consists of small cylindrical grains of smokeless powder with an extremely high burning rate. A maximum charge consists of six silk bags, each filled with 110 pounds (50 kg) of propellant.[5]

Furthermore, their use at Casablanca was the only time that a fast battleship of the US Navy fired her guns in anger in the European theater.

In the second instance, as the primary armament of USS Washington (BB-56) these guns were employed against the Imperial Japanese Navy's Kirishima (a much older and less powerful ship, armed with 8 × 14-inch guns and originally built as a battlecruiser during World War I) during the Naval battle of Guadalcanal; this has been cited by historians as the only instance in World War II in which one American battleship actually sank an enemy battleship.[8] (While there was a battleship-versus-battleship engagement at Leyte Gulf, torpedoes rather than gunfire were largely regarded as being responsible for sinking the enemy battleships.) The Washington had the aid of a naval fire control computer—in this case the Ford Instrument Company Mark 8 Range Keeper analog computer used to direct the fire from the battleship's guns, taking into account several factors such as the speed of the targeted ship, the time it takes for a projectile to travel, and air resistance to the shells fired at a target. This gave the US Navy a major advantage in the Pacific War, as the Japanese did not develop radar or automated fire control to a comparable level (although they did have complex mechanical ballistics computers, which had been in use since World War I).[9]Washington was able to track and fire at targets at a greater range and with increased accuracy, as was demonstrated in November 1942, when she engaged Kirishima at a range of 8,400 yards (7,700 m) at night. Using her nine 16"/45 caliber Mark 6 guns, Washington fired 75 rounds of 16-inch AP shells and scored an incredible twenty heavy-caliber hits that critically damaged the Kirishima, which eventually sank.[9][10][11] During the same battle, South Dakota also fired off several salvos from her 16"/45 guns before she had to withdraw for repairs to a faulty circuit breaker.

The next US Navy battleship class, the Iowa class, did not fall under Treaty weight restrictions and allowed for additional displacement. However, in their original design, the General Board was incredulous that a tonnage increase of 10,000 long tons (10,000 t) would only allow the addition of 6 knots (11 km/h; 6.9 mph)s over the South Dakotas. Rather than retaining the 16"/45 caliber Mark 6 gun used in the South Dakotas, they ordered that future studies would have to include the more powerful (but heavier) 16"/50 caliber Mark 2 guns left over from the canceled Lexington-class battlecruisers and South Dakota-class battleships of the early 1920s. It also allowed the draft of the ships to be increased, meaning that the ships could be shortened (lowering weight) and the power reduced (since a narrower beam reduces drag).[12]

The Mark 2 50-caliber gun turret weighed some 400 long tons (410 t) more than the Mark 6 45 caliber did; the barbette size also had to be increased so the total weight gain was about 2,000 long tons (2,000 t), putting the ship at a total of 46,551 long tons (47,298 t)—well over the 45,000 long ton limit. An apparent savior appeared in a Bureau of Ordnance preliminary design for a turret that could carry the 50 caliber guns in a smaller barbette. This breakthrough was shown to the General Board as part of a series of designs on 2 June 1938.[13] Nonetheless, the Mark 7 gun still weighed about 239,000 pounds (108 000 kg) without the breech, or 267,900 pounds with the breech, considerably heavier than the Mark 6.[2]

The Mark 7 had a greater maximum range over the Mark 6: 23.64 miles (38.04 km) vs 22.829 miles (36.740 km). When firing the same conventional shell, the 16"/45 caliber Mark 6 gun used by the treaty battleships of the North Carolina and South Dakota classes had a slight advantage over the 16"/50 caliber Mark 7 gun on the Iowa class, when hitting deck armor—a shell from a 45 cal gun would be slower, meaning that it would have a steeper trajectory as it descended. At 35,000 yards (20 mi; 32 km), a shell from a 45 cal would strike a ship at an angle of 45.2 degrees, as opposed to 36 degrees with the 50 cal.[2][3][4]

During World War II, the Mark 7 guns were only used for shore bombardment in the Pacific, while the Mark 6 guns also saw ship-to-ship combat in both the Pacific and European theaters. This was attributed to the fact that ships mounting the Mark 7 batteries, the Iowa class, were commissioned later than the Mark 6-equipped North Carolina and South Dakota classes, so they missed the Naval Battles of Casablanca and the Guadalcanal, one of the few instances where the US Navy's fast battleships were deployed for ship-to-ship combat. Most large scale naval battles involving the US Navy were fought by carrier-based aircraft in the Pacific.

1.
USS South Dakota (BB-57)
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USS South Dakota was a battleship in the United States Navy, in active service from 1942 until 1947. The lead ship of her class, South Dakota was the ship of the US Navy to be named in honor of the 40th state. The four ships of the class are considered to be the most efficient battleships designed under the limitations of the Washington Naval Treaty, in May 1943, South Dakota joined British Home Fleet patrols in the North Atlantic and Arctic Oceans before sailing again to the Pacific in August 1943. There, South Dakota participated in combat operations preparatory to the invasion of Japan until returning to the United States in October 1945 and her keel was laid down on 5 July 1939, at Camden, New Jersey, by the New York Shipbuilding Corporation. She was launched on 7 June 1941, sponsored by Mrs. Harlan J. Bushfield, wife of the Governor of South Dakota, and commissioned on 20 March 1942, with Captain Thomas Leigh Gatch in command. South Dakota differed from her sister ships in being constructed with only eight rather than ten twin 5/38 gun mounts, South Dakota fitted out at Philadelphia as a force flagship, and held shakedown training from 3 June through 26 July 1942. The battleship stood out of Philadelphia Navy Yard and sailed for the Panama Canal on 16 August, South Dakota served two tours in the Pacific Theater, with one tour with the British Home Fleet in between. On 12 September, the battleship set sail for the Pearl Harbor Navy Yard to receive repairs, on 12 October 1942, South Dakota was ready for sea service, and began training with Task Force 16, built around the aircraft carrier Enterprise. On 16 October, the force left Pearl Harbor to join Task Force 17, centered on the aircraft carrier Hornet, northeast of Espiritu Santo. The combined force, operating as Task Force 61 under Rear Admiral Thomas C, kinkaid, was ordered to make a sweep of the Santa Cruz Islands and then move southwest to block any Japanese naval forces that may be approaching to recapture Guadalcanal. US Navy PBY Catalina patrol bombers sighted a Japanese carrier force at noon on 25 October, early the next morning, when all carrier forces were within striking range, a Japanese scout plane spotted the American naval force, triggering the Battle of Santa Cruz. South Dakota and the Enterprise group were approximately 10 mi from Hornet group when the battle began, the first Japanese air attack was concentrated against Hornet. South Dakota operated near Enterprise to provide it protective fire against enemy aircraft, at 1045, TF16 was attacked by a group of Japanese dive bombers. Approximately an hour later the force was attacked again, this time by some 40 Japanese torpedo bombers. A third Japanese aerial assault was made by both bombers and torpedo bombers, coming in at 1230. South Dakota suffered a 550 lb bomb hit on top of its number one turret, when combat action was broken off that evening, the American naval forces retired toward Nouméa, New Caledonia. South Dakota was credited with downing 26 Japanese planes, firing 890 rounds of 5 inch,4,000 rounds of 40mm,3,000 rounds of 1.1 inch and 52,000 rounds of 20mm ammunition during the action. Captain Gatch made the assessment of the relative effectiveness of each weapon type in bringing down enemy aircraft during the action,5 inch, 5%, 40mm and 1.1 inch, 30% and 20mm

2.
Gun barrel
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A gun barrel is a part of firearms and artillery pieces. The hollow interior of the barrel is called the bore, a gun barrel must be able to hold in the expanding gas produced by the propellants to ensure that optimum muzzle velocity is attained by the projectile as it is being pushed out by the expanding gas. Modern small arms barrels are made of known and tested to withstand the pressures involved. Artillery pieces are made by various techniques providing reliably sufficient strength, early firearms were muzzle-loading, with powder, and then shot loaded from the muzzle, capable of only a low rate of fire. During the 19th century effective mechanical locks were invented that sealed a breech-loading weapon against the escape of propellant gases, the early Chinese, the inventors of gunpowder, used bamboo, a naturally tubular stalk, as the first barrels in gunpowder projectile weapons. Early European guns were made of iron, usually with several strengthening bands of the metal wrapped around circular wrought iron rings. The Chinese were the first to master cast-iron cannon barrels, early cannon barrels were very thick for their caliber. Bore evacuator Bore snake Cannon Muzzle Polygonal rifling Rifling Slug barrel Smoothbore

3.
Shell (projectile)
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A shell is a payload-carrying projectile that, as opposed to shot, contains an explosive or other filling, though modern usage sometimes includes large solid projectiles properly termed shot. Solid shot may contain a pyrotechnic compound if a tracer or spotting charge is used, originally, it was called a bombshell, but shell has come to be unambiguous in a military context. Words cognate with grenade are still used for an artillery or mortar projectile in some European languages, shells are usually large-calibre projectiles fired by artillery, combat vehicles, and warships. Shells usually have the shape of a cylinder topped by a nose for good aerodynamic performance, possibly with a tapering base. Solid cannonballs did not need a fuse, but hollow munitions filled with something such as gunpowder to fragment the ball, needed a fuse, percussion fuses with a spherical projectile presented a challenge because there was no way of ensuring that the impact mechanism hit the target. Therefore, shells needed a fuse that was ignited before or during firing. The earliest record of shells being used in combat was by the Republic of Venice at Jadra in 1376, shells with fuses were used at the 1421 siege of St Boniface in Corsica. These were two hollowed hemispheres of stone or bronze held together by an iron hoop, as described in their book, these hollow, gunpowder-packed shells were made of cast iron. At least since the 16th Century grenades made of ceramics or glass were in use in Central Europe, a hoard of several hundred ceramic greandes were discovered during building works in front of a bastion of the Bavarian City of Ingolstadt, Germany dated to the 17th Century. Lots of the grenades obtained their orignal blackpowder loads and igniters, most probably the grenades were intentionally dumped the moat of the bastion before the year 1723. Early powder burning fuses had to be loaded fuse down to be ignited by firing or a portfire put down the barrel to light the fuse, other shells were wrapped in bitumen cloth, which would ignite during the firing and in turn ignite a powder fuse. Nevertheless, shells came into use in the 16th Century. By the 18th Century, it was known that the fuse towards the muzzle could be lit by the flash through the windage between the shell and the barrel, the use of exploding shells from field artillery became relatively commonplace from early in the 19th century. Until the mid 19th century, shells remained as simple exploding spheres that used gunpowder and they were usually made of cast iron, but bronze, lead, brass and even glass shell casings were experimented with. The word bomb encompassed them at the time, as heard in the lyrics of The Star-Spangled Banner, typically, the thickness of the metal body was about a sixth of their diameter and they were about two thirds the weight of solid shot of the same calibre. To ensure that shells were loaded with their fuses towards the muzzle, in 1819, a committee of British artillery officers recognised that they were essential stores and in 1830 Britain standardised sabot thickness as a half inch. The sabot was also intended to reduce jamming during loading, despite the use of exploding shell, the use of smoothbore cannons, firing spherical projectiles of shot, remained the dominant artillery method until the 1850s. By the late 18th century, artillery could use canister shot to defend itself from infantry or cavalry attack and this involved loading a tin or canvas container filled with small iron or lead balls instead of the usual cannonball

4.
Recoil
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Recoil is the backward movement of a gun when it is discharged. To apply this counter-recoiling force, modern mounted guns may employ recoil buffering comprising springs and hydraulic recoil mechanisms, early cannons used systems of ropes along with rolling or sliding friction to provide forces to slow the recoiling cannon to a stop. Recoil buffering allows the maximum counter-recoil force to be lowered so that strength limitations of the gun mount are not exceeded, however, the same pressures acting on the base of the projectile are acting on the rear face of the gun chamber, accelerating the gun rearward during firing. This results in the required counter-recoiling force being proportionally lower, modern cannons also employ muzzle brakes very effectively to redirect some of the propellant gasses rearward after projectile exit. This provides a force to the barrel, allowing the buffering system. The same physics affecting recoil in mounted guns and cannons applies to hand-held guns, hands, arms and shoulders have considerable strength and elasticity for this purpose, up to certain practical limits. For this reason, establishing recoil safety standards for small arms remains challenging, a change in momentum of a mass requires a force, according to Newtons first law, known as the law of inertia, inertia simply being another term for mass. That force, applied to a mass, creates an acceleration, according to Newtons second law, the law of momentum -- changing the velocity of the mass changes its momentum. It is important to understand at this point that velocity is not simply speed, velocity is the speed of a mass in a particular direction. In a very technical sense, speed is a scalar, a magnitude, in summation, the total momentum of the system equals zero, surprisingly just as it did before the trigger was pulled. There are two conservation laws at work when a gun is fired, conservation of momentum and conservation of energy, recoil is explained by the law of conservation of momentum, and so it is easier to discuss it separately from energy. The nature of the process is determined by the force of the expanding gases in the barrel upon the gun. It is also determined by the force applied to the gun. The recoil force only acts during the time that the ejecta are still in the barrel of the gun, except for the case of zero-recoil, the counter-recoil force is smaller than the recoil force but lasts for a longer time. Since the recoil force and the force are not matched. In the zero-recoil case, the two forces are matched and the gun will not move when fired. In most cases, a gun is very close to a free-recoil condition, an example of near zero-recoil would be a gun securely clamped to a massive or well-anchored table, or supported from behind by a massive wall. For example, placing the butt of a large caliber gun directly against a wall, the recoil of a firearm, whether large or small, is a result of the law of conservation of momentum

5.
North Carolina-class battleship
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The North Carolina class was a class of two fast battleships, North Carolina and Washington, built for the United States Navy in the late 1930s and early 1940s. However, the acting Secretary of the Navy authorized a modified version of a different design and this called for a 27-knot ship with twelve 14-inch guns in quadruple turrets and protection against guns of the same caliber. In a major departure from traditional American design practices, this design accepted lower speed, North Carolina shot down between seven and fourteen Japanese aircraft in the Battle of the Eastern Solomons, and later sustained a torpedo hit from a Japanese submarine. In February 1944, Washington crushed its bow in a collision with battleship Indiana, following repairs, Washington rejoined her sister for the Battle of the Philippine Sea. After the end of the war, both took part in Operation Magic Carpet, the withdrawal of American military personnel from overseas deployments. The vessels were laid up in the fleet until the early 1960s, when North Carolina was sold to her home state as a museum ship. After the end of the First World War, several navies continued and expanded naval construction programs that they had started during the conflict, the United Kingdom was in the final stages of ordering eight capital ships. Imperial Japan was, by 1920, attempting to build up to an 8-8 standard with the Nagato, Tosa, Amagi, Kii and Number 13 classes. Two ships from these designs would be laid down per year until 1928. C. to discuss, and hopefully end, the subsequent Washington Naval Conference resulted in the 1922 Washington Naval Treaty. Along with many provisions, it limited all future battleships to a standard displacement of 35,000 long tons. It also decreed that the five countries could not construct another capital ship for ten years, the 1936 Second London Naval Treaty, while superseding the 1922 agreement, nonetheless kept many of the same requirements, though it restricted gun size on new warships to 14–inch. The General Board began preparations for a new class of battleships in May–July 1935, a was the only one to remain within the 35, 000–tons displacement limit set in the Washington Naval Treaty and reaffirmed in the Second London Naval Treaty. Although these original three studies were all fast battleships, the General Board was not definitively committed to the maximum speeds. Designs D and E were attempts at fast battleships with 16-inch guns and protections against the same, Design F was a radical attempt at a hybrid battleship-carrier, with three catapults mounted fore and eight 14-inch guns aft. However, the General Board finally decided to use faster ships and these studies demonstrated the difficulty the designers faced. Preliminary Design drew up five more studies in October, based upon either A with additional armor or a scaled-down B, all utilized 14-inch guns, Two called for four turrets, but this would be too heavy and mount less armor. Another, K, 15-inch belt and 5. 25-inch deck, while K was liked by the naval constructors, its designed standard displacement of 35,000 tons left little room for error or any modifications and improvements to the design. A final two, L and M, would use quadruple turrets to save weight while still mounting 12 guns, many officers in the United States Navy supported the construction of three or four battlecruiser-type ships for carrier escorts and to counter Japans Kongō class

6.
Battleship
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A battleship is a large armored warship with a main battery consisting of large caliber guns. During the late 19th and early 20th centuries the battleship was the most powerful type of warship, the word battleship was coined around 1794 and is a contraction of the phrase line-of-battle ship, the dominant wooden warship during the Age of Sail. The term came into use in the late 1880s to describe a type of ironclad warship. In 1906, the commissioning of HMS Dreadnought heralded a revolution in battleship design, subsequent battleship designs, influenced by HMS Dreadnought, were referred to as dreadnoughts. Battleships were a symbol of naval dominance and national might, the launch of Dreadnought in 1906 commenced a new naval arms race. Jutland was the largest naval battle and the only full-scale clash of battleships in the war, the Naval Treaties of the 1920s and 1930s limited the number of battleships, though technical innovation in battleship design continued. The value of the battleship has been questioned, even during their heyday, there were few of the decisive fleet battles that battleship proponents expected, and used to justify the vast resources spent on building battlefleets. Battleships were retained by the United States Navy into the Cold War for fire support purposes before being stricken from the U. S. Naval Vessel Register in the 2000s. A ship of the line was a large, unarmored wooden sailing ship which mounted a battery of up to 120 smoothbore guns, from 1794, the alternative term line of battle ship was contracted to battle ship or battleship. The sheer number of guns fired broadside meant a sail battleship could wreck any wooden enemy, holing her hull, knocking down masts, wrecking her rigging, and killing her crew. However, the range of the guns was as little as a few hundred yards. The first major change to the ship of the concept was the introduction of steam power as an auxiliary propulsion system. Steam power was introduced to the navy in the first half of the 19th century, initially for small craft. The French Navy introduced steam to the line of battle with the 90-gun Napoléon in 1850—the first true steam battleship, Napoléon was armed as a conventional ship-of-the-line, but her steam engines could give her a speed of 12 knots, regardless of the wind condition. This was a decisive advantage in a naval engagement. The introduction of steam accelerated the growth in size of battleships, the adoption of steam power was only one of a number of technological advances which revolutionized warship design in the 19th century. The ship of the line was overtaken by the ironclad, powered by steam, protected by metal armor, and armed with guns firing high-explosive shells. In the Crimean War, six ships and two frigates of the Russian Black Sea Fleet destroyed seven Turkish frigates and three corvettes with explosive shells at the Battle of Sinop in 1853

7.
South Dakota-class battleship (1939)
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The South Dakota class was a group of four fast battleships built by the United States Navy. They were the class of battleships to be named after the 40th state. The class comprised four ships, South Dakota, Indiana, Massachusetts and they were more compact and better protected than the preceding North Carolina class, but had the same main battery, nine 16/45 caliber Mark 6 guns in three-gun turrets. The ships can be distinguished from the earlier vessels by their single funnel. According to authors William Garzke and Robert Dulin, the South Dakota design was the best treaty battleship ever built, construction began shortly before World War II, with Fiscal Year 1939 appropriations. All four ships were retired post-war, South Dakota and Indiana were scrapped, Massachusetts, the preceding two North Carolina-class battleships had been assigned to the FY1937 building program, and in 1936, the General Board met to discuss the two battleships to be allocated to FY1938. The General Board argued for two more North Carolinas, but Admiral William H. Standley, the Chief of Naval Operations and that meant construction could not begin by 1938, so the ships were assigned to FY1939. Design work started in March 1937 and the draft for two battleships was formally approved by the Secretary of the Navy on 23 June, more specific characteristics for the two ships were ironed out, and those were approved on 4 January 1938. The ships were ordered on 4 April 1938. There was a deal of debate on the requirements for the new battleships. The belt armor was a much more problem, the 16-inch gun could penetrate 13.5 inches of plate. To mitigate this problem, sloped armor was proposed, it was infeasible to use inclined armor in an external belt, to minimize the drawbacks of the inclined belt, it sloped outward from the keel, then back in towards the armored deck. This meant that shells fired at close range would hit the upper portion of the belt at an angle. It did reduce the area that needed to be covered by the armored deck and this enabled the upper belt to be thicker, which to an extent ameliorated the vulnerability to plunging fire. Because the belt was internal, it provided the opportunity to extend it to the portion of the double bottom. Ultimately, the complex double incline belt armor was abandoned when it became apparent that a single slanted belt could provide similar protection, and save several hundred tons of weight. The size of the hull was also a problem, a longer hull generally equates to a top speed. In order to keep a top speed on a shorter hull

8.
Colorado-class battleship
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The Colorado-class battleships were a group of four battleships built by the United States Navy after World War I. However, only three of the ships were completed, Colorado, Maryland, and West Virginia, the fourth, Washington, was over 75% completed when she was canceled under the terms of the Washington Naval Treaty in 1922. As such, the Colorado-class ships were the last and most powerful battleships built by the US Navy until the North Carolina class entered service on the eve of World War II. The Colorados were the group of Standard-type battleships, designed to have similar speed. Apart from an upgrade in striking power to eight 16-inch guns, the Colorados were also the last American capital ships built with four turrets and twin-mounted guns. The change to larger guns was prompted by the Japanese Nagato-class battleships, all three ships had extensive careers during World War II. Maryland and West Virginia were both present during the attack on Pearl Harbor on 7 December 1941, Maryland escaped relatively unscathed, West Virginia was sunk in the shallow waters of the harbor but subsequently raised and repaired. All three ships served as support ships during amphibious operations. Maryland and West Virginia were present at the last surface action between battleships, the Battle of Surigao Strait during the Battle of Leyte Gulf in October 1944, the three ships, put into the reserve fleet after the end of the war, were scrapped by the late 1950s. This weapon dominated the design of battleships between 1913 and 1916, just as the 14-inch gun had dictated designs from 1908 to 1910, for this reason, he restricted the Bureau of Ordnance to proceed no further than blueprints for the new gun as a hedge against foreign developments. He finally approved construction of gun in October 1912 and the weapon was test fired successfully in August 1914. Such a move meant an increase of 8,000 tons per ship, debate continued for the next three years. Each year, President Woodrow Wilsons secretary of the navy, Josephus Daniels, balked at the increase in cost. Daniels finally compromised with the 1917 design battleships by allowing their armament to be upgraded and this, however, was to be the only substantial change to be allowed. This similarity would carry over into the Lexington and South Dakota classes as the United States Navy increasingly standardized its capital ship designs. This was partly the result of experience, when over 250 destroyers. The U. S. Navy had done this by a process almost akin to the assembly line, since the Naval Act of 1916 meant the imminent construction of 16 battleships and six battlecruisers, it was necessary to streamline production to save time and labor. Nevertheless, while US battleships were standardized as much as possible, most of the changes in the Tennessees were incorporated prior to any of their keels being laid

9.
Alaska-class cruiser
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The Alaska class was a class of six large cruisers ordered before World War II for the United States Navy. They were officially classed as large cruisers, but others have regarded them as battlecruisers and they were all named after territories or insular areas of the United States, signifying their intermediate status between larger battleships and smaller heavy and light cruisers. Of the six planned, two were completed, the construction was suspended on 16 April 1947, and the last three were canceled. Alaska and Guam served with the U. S. Navy for the last year of World War II as bombardment ships and they were decommissioned in 1947 after spending only 32 and 29 months in service, respectively. The idea for a large cruiser class originated in the early 1930s when the U. S. Navy sought to counter Deutschland-class pocket battleships being launched by Germany, up until the Alaska class, US cruisers designed between the wars followed this pattern. The initial impetus for the Alaska design came from the deployments of Germanys so-called pocket battleships in the early 1930s, while these claims are difficult to verify, they have led to the speculation that their design was politically motivated. One historian described the process of the Alaska class as torturous due to the numerous changes and modifications made to the ships layouts by numerous departments. The General Board, in an attempt to keep the displacement under 25,000 tons, as a result, the Alaska class, when built, were vulnerable to torpedoes and shells that fell short of the ship. The final design was a scaled-up Baltimore class that had the machinery as the Essex-class aircraft carriers. This ship combined a main armament of nine 12-inch guns with protection against 10-inch gunfire into a hull that was capable of 33 knots, the Alaskas were officially funded in September 1940 along with a plethora of other ships as a part of the Two-Ocean Navy Act. Their role had been altered slightly, in addition to their surface-to-surface role, yet another drastic change was considered during the carrier panic in late 1941, when the Navy realized that they needed more aircraft carriers as quickly as possible. Many hulls currently under construction were considered for conversion into carriers, in addition, the large cruiser design did not include the massive underwater protections found in normal carriers due to the armor weight devoted to counter shell fire. Lastly, an Alaska conversion could not satisfy the goal of having new aircraft carriers quickly. With this in mind, all planning to convert the Alaskas was abandoned on 7 January 1942, of the six Alaska-class cruisers that were planned, only three were laid down. The first two, Alaska and Guam, were completed, construction of Hawaii, the third, was suspended on 16 April 1947 when she was 84% complete. As a result, construction of the last three members of the class never began, and they were canceled on 24 June 1943. Alaska and Guam served with the U. S. Navy during the last year of World War II, similar to the Iowa-class fast battleships, their speed made them useful as shore bombardment ships and fast carrier escorts. Both protected Franklin when she was on her way to be repaired in Guam after being hit by two Japanese bombs

10.
Gauge (bore diameter)
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The gauge of a firearm is a unit of measurement used to express the inner diameter of the barrel. Thus there are twelve 12-gauge balls per pound, etc, the term is related to the measurement of cannon, which were also measured by the weight of their iron round shot, an 8 pounder would fire an 8 lb ball. These very large rifles, sometimes called elephant guns, were intended for use in India, gauge is abbreviated ga. ga, or G. The space between the number and the abbreviation is often left out, as in 12ga. Therefore, a shotgun or n-bore rifle has a bore diameter of approximately d n =11.33 Explanation. Divide it by 11.3 to find the volume of the ball, multiply it by 0.75 and divide it by pi, then find its cube root, to find its radius in cm. Multiply it by 2 to find the diameter in cm, Divide it by 2.54 to find the diameter in inches. This simplifies to d n =1.67 / n 3 to find the diameter in inches of the barrel of an n-gauge shotgun. Therefore, if the diameter is in inches, n =4.66 / d n 3 Another source for a gauge size formula can be found in page Shotgun shell#Shotgun gauge diameter formula. Since shotguns were not originally intended to fire projectiles, but rather a compressible mass of shot. The fact that most shotgun bores are not cylindrical also causes deviations from the bore diameter. The chamber of the gun is larger, to accommodate the thickness of the walls. The forcing cone can be as short as a fraction of an inch, or as long as a few inches on some guns. At the muzzle end of the barrel, the choke can constrict the bore even further, so measuring the diameter of a shotgun is not a simple process. Shotgun bores are commonly overbored or backbored, meaning that most of the bore is larger than the value given by the formula. This is claimed to reduce recoil and improve patterning. A 12-gauge shotgun, nominally 18.5 mm, can range from a tight 18.3 mm to an extreme overbore of 20.3 mm. Some also claim an increased velocity with the barrels, up to 15 m/s

11.
Rifling
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In firearms, rifling consists of helical grooves in the internal surface of a guns barrel, which impart a spin to a projectile around its long axis. This spin serves to stabilize the projectile, improving its aerodynamic stability. Rifling is often described by its twist rate, which indicates the distance the rifling takes to complete one revolution, such as 1 turn in 10 inches. A shorter distance indicates a faster twist, meaning that for a given velocity the projectile will be rotating at a spin rate. Barrels intended for long, small-diameter bullets, such as the ultra-low-drag, 80-grain 0.223 inch bullets, extremely long projectiles such as flechettes may require high twist rates, these projectiles must be inherently stable, and are often fired from a smoothbore barrel. Muskets were smoothbore, large caliber weapons using ball-shaped ammunition fired at low velocity. Due to the high cost and great difficulty of manufacturing, and the need to load readily from the muzzle. Consequently, on firing the ball bounced off the sides of the barrel when fired, barrel rifling was invented in Augsburg, Germany in 1498. In 1520 August Kotter, an armourer of Nuremberg, Germany improved upon this work, though true rifling dates from the mid-16th century, it did not become commonplace until the nineteenth century. The most successful weapons using rifling with black powder were breech loaders such as the Queen Anne pistol, the grooves most commonly used in modern rifling have fairly sharp edges. More recently, polygonal rifling, a throwback to the earliest types of rifling, has become popular, polygonal barrels tend to have longer service lives because the reduction of the sharp edges of the land reduces erosion of the barrel. Supporters of polygonal rifling also claim higher velocities and greater accuracy, polygonal rifling is currently seen on pistols from CZ, Heckler & Koch, Glock, Tanfoglio, and Kahr Arms, as well as the Desert Eagle. Such guns have achieved significant increases in velocity and range. Examples include the South African G5 and the German PzH2000, gain-twist rifling begins with very little change in the projectiles angular momentum during the first few inches of bullet travel after ignition during the transition from chamber to throat. This enables the bullet to remain undisturbed and trued to the case mouth. After engaging the rifling the bullet is progressively subjected to accelerated angular momentum as burning powder propels it down the barrel. By only gradually increasing the rate, torque is spread along a much longer section of barrel. Gain-twist rifling was used as early as the American Civil War, colt Army and Navy revolvers both employed gain-twist rifling

12.
Yamato-class battleship
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The Yamato-class battleships were battleships of the Imperial Japanese Navy constructed and operated during World War II. Displacing 72,000 long tons at load, the vessels were the heaviest battleships ever constructed. The class carried the largest naval artillery ever fitted to a warship, nine 460-millimetre naval guns, two battleships of the class were completed, while a third was converted to an aircraft carrier during construction. Musashi was sunk during the battle by American carrier airplanes, Shinano was sunk ten days after her commissioning in November 1944 by the submarine USS Archerfish, while Yamato was sunk by US naval air power in April 1945 during Operation Ten-Go. Their question to answer was, What were designs and specifications for a powerful enough to intimidate likely adversaries. Programs that had begun during the conflict, and, that were now inspired by the lessons learned. The subsequent Washington Naval Conference resulted in the Washington Naval Treaty, lastly, the treaty did not proportionately reduce fleet sizes equally for the Japanese Navy in the Pacific theater. But the reductions were to the ratio of,5,5,3. This meant the scrapping of existing or planned capital ships to give a 5,5,3,1.75,1.75 ratio of tonnage with Britain, Japan accepted this, but seriously resented it. In the 1930s, the Japanese government began a shift towards ultranationalist militancy and this movement called for the expansion of the Japanese Empire to include much of the Pacific Ocean and Southeast Asia. The maintenance of such an empire—spanning 3,000 miles from China to Midway Island—required a sizable fleet capable of sustained control of territory and this modernization included, among other things, additional speed and firepower, which the Japanese intended to use to conquer and defend their aspired-to empire. When Japan withdrew from the League of Nations in 1934 over the Mukden Incident, Japan would no longer design battleships within the treaty limitations and was free to build warships larger than those of the other major maritime powers. The U. S. possessed significantly greater power than Japan. Furthermore, several leading members of the United States Congress had pledged to outbuild Japan three to one in a naval race. Each of these battleships would be capable of engaging multiple enemy capital ships simultaneously and these early plans varied greatly in armament, propulsion, endurance, and armor. Main batteries fluctuated between 460 mm and 406 mm guns, while the secondary armaments were composed of differing numbers of 155 mm,127 mm, propulsion in most of the designs was a hybrid diesel-turbine combination, though one relied solely on diesel and another planned for only turbines. Endurance in the designs had, at 18 kn, a low of 6,000 nmi in design A-140-J2 to a high of 9,200 nmi in designs A-140A, armor varied between providing protection from the fire of 406 mm guns to enough protection against 460 mm guns. After these had been reviewed, two of the original twenty-four were finalized as possibilities, A-140-F3 and A-140-F4, differing primarily in their range, they were used in the formation of the final preliminary study, which was finished on 20 July 1936